The production of polyurethanes using catalysts containing tertiary amino groups is known. Although a high standard of polyurethane foaming technology has been achieved thereby, practice has shown that improvements are still possible.
Gelling of the foam is usually achieved with a combination of various catalysts, frequently using derivatives of morpholine. These catalysts are advantageously used for the formation of a fine, skin-like structure on the surface of the molded foam parts, for improving the hardening characteristics of the molded articles and for preventing flaws in the foam which occur in the course of the foaming process.
The morpholine derivatives hitherto used have been mainly N-methylmorpholine (NMM) and N-ethylmorpholine (NEM) and more recently dimethylaminoethylmorpholine (DMEM). It is found in foaming practice that when using NMM, NEM or DMEM, unpleasant odors still occur in the production of the foams and upon removal of the foam products from their molds.
The desired effects described above, however, have hitherto not been achievable without the use of these activators. It is therefore an object of the present invention to provide catalysts by which the advantageous characteristics of the activators hitherto used in this technology are preserved, especially as regards formation of the skin and the foaming characteristics, but the unpleasant evolution of odors is considerably reduced or even eliminated.